This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A360518 #18 Mar 22 2023 08:06:33 %S A360518 2,9,24,47,497,4997,49997,499997,4999997,49999997,499999997, %T A360518 4999999997,49999999997,499999999997,4999999999997,49999999999997, %U A360518 499999999999997,4999999999999997,49999999999999997,499999999999999997,4999999999999999997,49999999999999999997 %N A360518 Numbers j such that there exists a number i <= j with the property that i+j and i*j have the same decimal digits in reverse order. %C A360518 The pairs (i,j) are (2,2), (9,9), (3,24), (2,47), (2,497), (2,4997), (2,49997), (2,499997), (2,4999997), (2,49999997), ... %C A360518 These pairs, together with all pairs (2,4999..997), comprise the complete list. %D A360518 Xander Faber and Jon Grantham, "On Integers Whose Sum is the Reverse of their Product", Fib. Q., 61:1 (2023), 28-41. %H A360518 Xander Faber and Jon Grantham, <a href="https://arxiv.org/abs/2108.13441">On Integers Whose Sum is the Reverse of their Product</a>, arXiv:2108.13441 [math.NT], 2021. %H A360518 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10). %F A360518 G.f.: x*(220*x^4-127*x^3-55*x^2-13*x+2)/((10*x-1)*(x-1)). %F A360518 From _Stefano Spezia_, Mar 21 2023: (Start) %F A360518 a(n) = (10^n - 600)/200 for n > 3. %F A360518 E.g.f.: (1797 - 1800*exp(x) + 3*exp(10*x) + 2970*x + 3450*x^2 + 2200*x^3)/600. (End) %e A360518 2+497 = 499 and 2*497 = 994. %Y A360518 Cf. A276509. %K A360518 nonn,base,easy %O A360518 1,1 %A A360518 _N. J. A. Sloane_, Feb 27 2023